Could I be pregnant?

Hi everyone so I missed my period during may it was supposed to be here on may 20th. I had unprotected sex may 23rd I took plan b immediately after. It’s been over 10 days I took a few pregnancy tests and it’s coming out negative. Today I woke up and saw some brown discharge coming out as if I’m about to get my period but it hasn’t really started yet. Could I possibly be pregnant? Could this be implantation bleeding?